Method of and apparatus for obtaining flat metallic strip



M. D. STONE July 4, 1967 METHOD OF AND APPARATUS FOR OBTAINING FLAT METALLIC STRIP 4 Sheets-Sheet 1 Filed May 18, 1964 INVENTOR. MORRIS 0. STONE ATTORNEY.

M. D. STONE July- 4, 1967 METHOD OF AND APPARATUS FOR OBTAINING FLAT METALLIC STRIP Filed May 18, 1964 Q 4 Sheets-Sheet 2 INVENTOR. MORE/5 0. STONE X4 Q- M ATTORNEY.

July 4, 1967 M. D. STONE 3,328,992

METHOD OF AND APPARATUS FOR OBTAINING FLAT METALLIIC STRIP Filed May 1.8, 1964 4 Sheets-Sheet 5 INVENTOR. MORRIS D. 57" ONE ATTOR/VEY.

M. D. STONE July 4, 1967 METHOD OF AND APPARATUS FOR OBTAINING FLAT METALLIC STRIP Filed May 18, 1964 United States Patent Ofiice 3,328,992 Patented July 4, 1967 3,328,992 METHOD OF AND APPARATUS FOR OBTAINING FLAT METALLIC STRIP Morris D. Stone, Pittsburgh, Pa., assignor to United Engineering and Foundry Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed May 18, 1964, Ser. No. 368,243 Claims priority, application Great Britain, June 4, 1963, 22,141/ 63 8 Claims. (Cl. 72-205) This invention relates to a method of and apparatus for processing strip material and, more particularly, to the processing of metallic strip in a manner that its flatness is improved and/or controlled.

As used in this specification the term strip flatness, and similar expressions which are sometimes stated in negative language, refers to a strip characterized by being substantially free from buckles or waves, either transversal or longitudinal. In the rolling of metal strip, by design or otherwise, the strip is very often reduced in the manner wherein it has a varying cross-sectional thickness. One of the principal reasons for this condition is due to the fact that the rolls deflect under the rolling load so that the opposed rolling surfaces of the cooperating rolls, i.e., the surfaces that form the pass opening, do not conform properly to the cross-section of the entering strip. As a result certain transverse portions of the strip are subject to greater rolling pressure than other portions which condition elongates cetain portions of the strip more than others. This differential elongation causes waves or buckles to form in the strip, that is to say, the strip becomes non-flat, the extent and height of the waves being dependent upon the differences in the relative elongations across the width of the strip.

Two areas where non-flat strip is found to be seriously objectionable are in the rolling of strip for paneling, used for example in ofiice furniture, etc. and in the rolling of tinplate.

It is an object of the present invention to provide a method of and apparatus for imposing a tension stress distribution on a metallic strip while it is being reduced, say for example by a rolling mill, in such a manner and of such magnitude so as to reduce or remove the non-flatness of the strip.

It is a further object of this invention to provide a method and apparatus for imposing differential controlled tension stresses transversely of and to a strip while the strip is being rolled in a rolling mill, which tensions will act at the bite of the rolls and be so related to the non-flat condition of the strip so as to correct for the non-flatness thereof.

In one form of an apparatus built to practice the present invention, at the delivery side of a rolling mill a strip deflecting roll is provided between the mill and the windup reel, the reel being designed to impose a range of total tension forces upon the strip. Means are provided for deflecting the roll about its longitudinal axis in a manner to impose greater tension stresses in one or more transverse portions of the strip than in the other portions thereof, the portion or portions to which the greater tension stresses are imposed being the portion that possesses the greater tautness. The application of tension in this manner will have the effect of causing the thicker portions of the strip to be subject to a greater reduction than the thinner portion or portions thereof, thereby reducing the difference in the elongation between the portions which will have the effect of reducing or removing the non-flatness of the strip.

One form of the method of the present invention comprises a method of rolling fiat strip including the steps of passing a strip through a mill to reduce the thickness thereof, said strip during rolling being subject to differential elongation across its width, imposing differential tension stresses upon the strip across its width as it enters or leaves the mill or both, said differential tension stresses being so related to the existing differential elongation so as to reduce or eliminate the non-flatness of the strip otherwise caused by said existing differential elon-gations.

These and other features and advantages of the present invention will be more clearly seen from the following description when read in the light of the accompanying drawings of which:

FIGURE 1 is an elevational view of a deflector roll assembly incorporating the features of the present invention, wherein the related conventional processing equipment in shown in phantom;

FIGURE 2 is a plan view of the deflector roll assembly illustrated in FIGURE 1;

FIGURE 3 is an end view, partly in section, of the deflector roll assembly shown in the previous figures;

FIGURE 4 is an enlarged view of a substantial part of the deflector roll assembly illustrated in FIGURE 1;

FIGURE 5 is a diagram illustrating the deflections and application of the bending moments to the deflecting roll shown on the previous figures;

FIGURE 6 is an elevational view, partly in section, of a second embodiment of the invention; and

FIGURE 7 is a sectional view, taken on lines VII-VII of FIGURE -6.

With reference to the drawings and particularly FIG- URES l and 2, there is illustrated a cold rolling mill 10 which could be a temper or reduction mill, including a pair of cooperating working rolls 11 each having a backing up roll 12. It is believed unnecessary to show or describe the various other components of the mill or to describe the operation thereof since both are well known in the art, FIGURE 1 shows the delivery side of the mill, at which side a tension bridle 13 is provided consisting of rolls 14 and 15 around which the strip S may be optionally directed in a circuitous path. As shown, the strip can also be passed over the bridle, in which case the strip tension at the bite of the mill will be generated by other means such as a reel. Adjacent to the tension bridle 13 and opposite the mill side thereof a tension reel 17 is provided, the two circles concentric with the reel representing the first and last convolution of a coil C, respectively. Between the tension reel 17 and the tension bridle 13, there is arranged a strip deflecting roll assembly 18, built in accordance with the teachings of the present invention.

As shown in FIGURE 3, the strip deflecting roll assembly 18 consists of a framework 19 built up under the path of travel of the strip, having a centrally located beam 21 to which are secured equally spaced apart bearing' housings 22 and 23. These bearings housings rotatably support a strip deflector roll 25, the bearings dividing the roll into a center portion 26 and opposite end portions 27 and 28, the center portion 26 being the portion of the roll that engages the lower surface of the strip. Bearings 29 and 30 are secured to the ends of the portions 27 and 28 respectively, of the deflector roll 25 and have housings 31 and 32, the lower part of the housings being connected to mechanical jacks 33 and 34.

In still referring to FIGURE 3 and with respect to the end of the roll 25 illustrate-d on the left-hand side as one looks at the drawing, the mechanical jack 33 has a horizontal shaft 35 which is connected to a handwheel 36, the handwheel 36 passing through and is rotatable relative to a tubular section 37. The tubular section 37 is formed as a part of a second handwheel 38 which operates the jack 34 arranged on the right-hand side of FIGURE 3. The jack 34 and the handwheel 38 are connected together by means of a belt 39 which drivenly encircles a gear 41, the gear being mounted on the end of a shaft 42 which is connected to the mechanical jack 34. As shown in FIGURE 3, the deflector roll 25 is driven by a motor 43. The speed of the roll being maintained approximately equal to that of the strip. It will be seen from the above that by operating the jacks 33 and 34, the end portions 27 and 28 of the roll 25 will be deflected by the bending moment generated so that the center portion 26 is deflected toward or away from the strip S. FIGURE diagrammatically illustrates the deflection of the roll 25, the deflections of course being exaggerated for the purpose of illustration.

In order that the operator may be able to quickly determine the exact magnitude of the deflection of the roll 25, a gauge may be provided, one example of which is shown in FIGURES l and 4. To the end of the roll 25 a pointer 44 is provided, the outer end of which projects across a vertically arranged scale 45 which is mounted on a part of the framework 19. The calibration of the scale 45 represents the equivalent crown of the roll 25. In the illustrated form of the invention, it will be noted that the overhung portions 27 and 28 of the roll 25 are longer than one-half of the center portion 26 so that the ends of the rolls will deflect more than the center, enabling a more accurate scale to be employed.

It will be appreciated that while, for the purpose of illustration, jacks have been employed to impose bending moments upon the ends of the roll 25, other means and ways of applications of the bending moments may be used without departing from the spirit of the invention. It will also be appreciated that the deflector roll assembly may be arranged at the entry side of the mill. The employment of the tension bridle 13 will afford the advantage of maintaining very low tension between the reel 17 and bridle. This is very desirable since it reduces the effect that the eccentric rotation of the reel has on the flatness of the strip.

Reference will now be made to the basic theory of the present invention. As previously stated, it is an object of the invention to impose upon the strip transversely varying longitudinal tension stresses of such a character that during rolling the influence of said tension stresses will have the effect of reducing or eliminating non-flatness in the strip. Work thus far, has indicated that in working with medium carbon steel, tension stresses in a range of 0 to 25,000/35,000 lbs. per sq. inch are necessary to accomplish the result.

In determining the magnitude of the differential stress necessary, meaning by this term, the difference between the maximum and minimum longitudinal stresses desired in the strip, we have the equations:

S =strip tension differential L=strip length under tension AL=the amount of differential elastic stretch E=modules of elasticity Assuming that L=l20", and e=30 10 and S desired=30,000 lbs/sq. in. and solving for AL, we have the equation:

sd -L 30,000 120" From the above calculations it is seen that the strip deflector roll 25 must be designed to impose upon the strip, differential elastic stretches or strains of the order of approximately A". One arrangement that will very conveniently meet this condition has been illustrated in the drawings, wherein it will be noted that the relationship of the roll 25 and the reel 17 is such, and the strip is so conveyed to the reel for coiling thereon that the strip actually wraps around a portion of the roll 25 for its entire width. In considering the advantages in wrapping a=the angular wrap of strip around the roll 25, in degrees d=the amount of deflection of roll 25 (see FIGURE 5) D=the diameter of the roll 25 In solving for d, we start with the equation:

Now

from Equation 2, hence from which it follows that Sd/E a/57 .3

for a=60, then, we find that Thus, it can be seen that by providing a strip deflecting roll that may be deflected an amount up to the order of approximately A1" with a wrap angle of 60 degrees effective control of the tension distribution across the width of the strip can be obtained which will result in a corresponding differential in the thickness of the strip across its width during rolling, i.e., the higher the tension for a given roll opening, the greater the reduction taken. In the actual embodiment in the invention, thus far, it has been found that a relatively large deflection of the roll is necessary for the wrap angles used. In some arrangements the change in the angle of wrap a of the strip may prove to be significant, in which case the deflection of the roll can be changed to suit the particular conditions. It will be appreciated that in certain cases the roll 25 can be provided with a machine crown which may be made to augment the deflection imposed on the roll by bending.

FIGURES 6 and 7 illustrate a second embodiment of the present invention wherein there is provided a housing 46 for receiving readily adjustable rolls 47 and 48 which are carried by a common member and move as a unit. The top roll 47 is convexly shaped while the roll 48 is shaped concavely, the convexity and concavity being complements of each other. As indicated in FIG- URE 6, there is provided sufiicient space between the adjacent surfaces of the two rolls to permit a strip to pass between the -roll without contact being made. Means are provided for adjusting the rolls as a unit relative to the strip in a vertical direction such as a pair of screws 49. Piston cylinder assemblies 50 mounted at the top of the machine urge the rolls toward the screws 49. As shown in FIGURE 6, the rolls are adapted to be driven by drive shafts 51, which are connected to a source of power, not shown. In FIGURE 7 the housing 46 is located between a rolling mill 52 on the one side and a strip carrying roll 53 on the other.

By this arrangement the operator has the option of either engaging and deflecting the strip at its center portion or at its two ends, by either bringing the convex roll 47 downward toward the strip so that its center portion engages the center portion of the strip, or bringing the concave roll 48 upward so that its ends engage the two end portions of the strip. In the first case greater tension will be imposed on the center of the strip which will be used when the strip is taut at its center and wavy at the edges, and in the second case greater tensions will be imposed upon the edges of the strip, this arrangement being used when the edges of the strip are taut, and the center wavy.

From the above it can be seen that the present invention provides a method of rolling flat strip which of course could be rubber or plastic, etc. instead of metal, by imposing differential tensions upon the strip either before or after the strip has entered the bite of the mill, which tensions will influence the rolling action to cause greater reductions to be taken on certain portions of the strip transversely, whereby, the non-flatness of the strip will be reduced or eliminated. The present invention also provides an apparatus for carrying out the method. Of course, many other apparatuses can be employed to obtain the diiferential strains than the two forms herein illustrated.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my inve-ntion and have illustrated and described what I consider to represent the best embodiment thereof. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In combination with a device for reducing the thickness of strip-like material and a device for imposing a tension force on the material as it passes through the reducing device:

a material deflecting roll arranged between said two devices comprising a central body portion and two opposite end portions, and wherein the body portion is arcuately deflectable between said end portions and engageable with one surface of said material,

force generating means connectable to said two opposite end portions of said roll to impose bending moments on the roll to cause the material to assume an arcuate shape whereby transversely'varying tension stresses are imposed on the material.

2. In a device, according to claim 1, including a gauge for indicating the magnitude of the deflection of said roll.

3. In a device, according to claim 1,

means for driving said roll at a speed approximately equal to the speed of the material.

4. In a device, according to claim 1, wherein said roll is rotatably supported by a pair of inner spaced-apart bearings and by a pair of outer spaced-apart bearings,

a force generating means connected to each of said outer bearings.

5. In combination with a device for reducing the thickness of strip-like material and a device for imposing a tension force on the material as it passes in a given direction through the reducing device;

a pair of rolls arranged in a common plane to allow said material to pass therebetween,

means for rotatably supporting said rolls, said rolls being constructed and arranged so that in one position the material can be passed between them without any appreciable deflection away from the given direction,

one of said rolls being convexly shaped to engage the center portion of the material,

the other of said rolls being concavely shaped to engage the opposite edges of the material, and

means for bringing one of said rolls into engagement with the material.

6. In a device, according to claim 5, including means for adjusting the rolls as a unit relative to the material.

7. In a method for correcting for non-flatness in a strip being reduced, wherein there is arranged in sequence means for tensioning the strip, variable crown deflector roll-engageable with and for deflecting the strip out of a first path of travel and a strip reducing apparatus, comprising the steps of:

imposing a tension force on the strip by said tensioning means while the strip is being reduced by said reduclng apparatus,

causing one surface of the strip to be engaged by said roll to cause the strip to assume the shape of the roll in its transverse direction,

varying the effective crown of said roll and, hence, the

shape of the strip depending on the degree of nonflatness of the strip, in which the combined effect of the tension force imposed on the stri and the crown of the roll subjects the strip to a controlled transverse distribution of longitudinal tension stresses which are of sufficient magnitude to vary transversely the elongations of the strip being reduced.

8. In a method for correcting for non-flatness in a strip according to claim 7,

wherein said step of varying the effective crown of said r-oll comprises applying a controlled bending moment to said variable crown deflector roll.

References Cited UNITED STATES PATENTS 495,147 4/1893 Barraclough 72-179 2,250,541 7/1941 Lessmann 72-205 3,136,184 6/1964 Wells 72-205 3,206,961 9/ 1965 Bailey 72-205 XR 3,253,445 5/1966 Franek 72-205 XR FOREIGN PATENTS 707,116 4/ 1965 Canada.

CHARLES W. LANHAM, Primary Examiner. A. RUDERMAN, Assistant Examiner. 

7. IN A METHOD FOR CORRECTING FOR NON-FLATNESS IN A STRIP BEING REDUCED, WHEREIN THERE IS ARRANGED IN SEQUENCE MEANS FOR TENSIONING THE STRIP, VARIABLE CROWN DEFLECTOR ROLL ENGAGEABLE WITH AND FOR DEFLECTING THE STRIP OUT OF A FIRST PATH OF TRAVEL AND A STRIP REDUCING APPARATUS, COMPRISING THE STEPS OF: IMPOSING A TENSION FORCE ON THE STRIP BY SAID TENSIONING MEANS WHILE THE STRIP IS BEING REDUCED BY SAID REDUCING APPARATUS, CAUSING ONE SURFACE OF THE STRIP TO BE ENGAGED BY SAID ROLL TO CAUSE THE STRIP TO ASSUME THE SHAPE OF THE ROLL IN ITS TRANSVERSE DIRECTION, VARYING THE EFFECTIVE CROWN OF SAID ROLL AND, HENCE, THE SHAPE OF THE STRIP DEPENDING ON THE DEGREE OF NONFLATNESS OF THE STRIP, IN WHICH THE COMBINED EFFECT OF THE TENSION FORCE IMPOSED ON THE STRIP AND THE CROWN OF THE ROLL SUBJECTS THE STRIP TO A CONTROLLED TRANSVERSE DISTRIBUTION OF LONGITUDINAL TENSION STRESSES WHICH ARE OF SUFFICIENT MAGNITUDE TO VARY TRANSVERSELY THE ELONGATIONS OF THE STRIP BEING REDUCED. 